I had a similar issue when I was trying to install. I had Solus installed, and it would see the Solus partitions and the nvme drive, but I couldn’t install to my nvme, just overwrite the Solus partitions, keeping the same ext4, swap size, and everything. I used gparted to erase and reformat the whole drive as an ntfs partition, then I was able to install with btrfs with no issue.